CF33-hNIS-anti-PD-L1 oncolytic virus followed by trastuzumab-deruxtecan in a patient with metastatic triple negative breast cancer: a case study

Prognosis of metastatic triple negative breast cancer (mTNBC) remains poor despite recent advances in therapeutic options. Trastuzumab deruxtecan (T-DXd) has shown promising efficacy in patients with human epidermal growth factor receptor 2 (HER2)-low breast cancer, which is defined by immunohistochemistry (IHC) 1+ or 2+ and lack of HER2 amplification by fluorescence in situ hybridization (FISH) testing. The purpose of the study is to evaluate the safety and initial evidence of efficacy of intratumoral administration of CF33-hNIS-anti-PD-L1 (CHECKvacc) against mTNBC. Oncolytic virus CHECKvacc intratumoral injection is currently undergoing investigation in patients with mTNBC as a single agent (NCT05081492). The patient was enrolled on the clinical trial CHECKvacc for the Treatment of Metastatic Triple Negative Breast Cancer, received a single dose of CHECKvacc, and discontinued the study due to lack of immediate response. We report a case of a patient with mTNBC who was heavily pretreated and presented with extensive dermal metastasis. Two dermal metastasis biopsies in 2021 showed HER2 0 by IHC. The patient received a single dose of CHECKvacc and discontinued the study due to lack of immediate response. Twenty-five days later, the patient received treatment with T-DXd, and her tumor regressed significantly. The patient's disease-free survival was 10 months (December 2021-October 2022). The sequential treatment with intratumoral injection of CHECKvacc followed by T-DXd may have significant clinical activity in select patients with heavily pretreated mTNBC. ClinicalTrials.gov NCT05081492.